How to connect two measuring instruments with RTD PT100

A thermal resistance.

Only one meter can be connected, if more than one meter display is required, the display instrument with voltage signal output can be selected, and multiple display meters can be connected in parallel at its output.

At present, there are three main ways of RTD leads.

1. Two-wire system: the way to connect a wire at both ends of the thermal resistance to draw out the resistance is called the two-wire system: this lead method is very simple, but because there must be a lead resistance R in connecting the wire, the size of R is related to the material and length of the wire, so this lead method is only suitable for occasions with low measurement accuracy.

2. Three-wire system: the way of connecting one lead wire at one end of the root of the thermal resistance and connecting two leads at the other end is called the three-wire system, which is usually used with the bridge, which can better eliminate the influence of the lead resistance, and is the most commonly used lead resistance in industrial process control.

3. Four-wire system: the way of connecting two wires at both ends of the root of the thermal resistance is called the four-wire system, in which two leads provide a constant current i for the thermal resistance, convert R into voltage U, and then lead U to the secondary instrument through the other two leads. It can be seen that this lead method can completely eliminate the resistance effect of the lead, and is mainly used for high-precision temperature detection.

The RTD adopts the three-wire connection method. The three-wire system is used to eliminate measurement errors caused by the resistance of the connected wires. This is because the circuit used to measure RTD is generally an unbalanced bridge.

As a bridge arm resistance of the bridge, the connecting wire (from the RTD to the center control room) also becomes part of the bridge arm resistance, which is unknown and varies with the ambient temperature, resulting in measurement errors. The three-wire system is adopted, one wire is connected to the power supply end of the bridge, and the remaining two are respectively connected to the bridge arm where the thermal resistance is located and the bridge arm adjacent to it, so that the measurement error caused by the resistance of the wire line is eliminated. In industry, the three-wire connection method is generally adopted.

Thermocouples produce millivolts, and there is no such problem.

The temperature range of the pt100 is -200 +850.

The resistance of the PT100 changes with the temperature. 100 after PT means that it has a resistance of 100 ohms at 0 and about ohms at 100.

How it works: when the pt100 is at 0 degrees Celsius, its resistance is 100 ohms, and its resistance will increase at an approximate uniform rate as the temperature rises. But the relationship between them should be closer to a parabola.

The formula for calculating the change of the resistance value of platinum resistance with the change of temperature:

2000 t<850 rt=r0(1+at+bt2) (2) rt is the resistance value at t, and r0 is the resistance value at 0. The coefficients a, b, and coefficients in the formula are experimentally determined.

Disconnect the PT100 in the circuit first, and then measure its resistance value with a multimeter resistance (200). But the measurement results can only judge whether the PT100 is good or bad. Take the blind pt100 in the god bureau 0 when the resistance value is 100, with the increase of temperature resistance value gradually increases, the specific correspondence can be viewed in its indexing table.

The corresponding indexing table can be searched in the appendix of the book or searched online.

Use a multimeter to measure that the two outputs (sometimes multi-end) are connected (although there is a certain resistance), and if the open circuit is undoubtedly bad, this is the first step when actually judging whether it is good or bad. The resistance value of RTD is certain, such as PT100 at about 110 ohms at room temperature, and CU50 at around 55 ohms at room temperature.

The three wires of the RTD are connected to terminals 1, 2 and 3.

First, if the display instrument has a wiring diagram, the wiring method is shown in the illustration.

Second, if there is no wiring diagram, the wiring method is as follows:

1. If there are two wires of the same color, connect the two wires of the same color to the No. 2 and No. 3 terminals, and the other one to the No. 1 terminal, if the display is not normal after the power is turned on (the maximum or minimum is displayed), the wire on the No. 1 terminal and the wire on the No. 3 terminal can be replaced.

2. If the color of the three wires is different, there will inevitably be one of the red, connect the red wire to the No. 1 terminal, and connect the remaining two wires to the No. 2 and No. 3 terminals, if the display is not normal after the power is turned on (the maximum or minimum is displayed), the wire on the No. 1 terminal and the wire on the No. 3 terminal can be replaced.

The wiring method of CU50 and RTD is the same as above.

The two wires of PT100 can be connected to the input terminal of the instrument, and the input type on the meter is generally set to PT100.

PT100 is a platinum RTD, and its resistance is proportional to the change in temperature. The relationship between the resistance value of PT100 and the temperature is as follows: when the temperature of PT100 is 0, its resistance value is 100 ohms, and at 100 its resistance value is about ohms.

Its industrial principle: when the PT100 is at 0 degrees Celsius, its resistance is 100 ohms, and its resistance will increase at a uniform rate as the temperature rises.

RTD is a type of sensor commonly used in temperature measurement. PT100 RTD is a platinum resistance that measures temperature based on the change in resistance value when the temperature changes. PT100 RTDs are widely used in industrial automation control because of their rapid response and high accuracy.

The measuring range of the PT100 RTD needs to be set on a case-by-case basis. Depending on the sensitivity of PT100 RTDs, they can measure in the range of -200 to 850, typically. This temperature range can cover many applications such as automated manufacturing, biology, energy monitoring, and many more.

In addition to the temperature range, the rated resistance value of the PT100 RTD is also a concern that should be concerned. The PT100 RTD is rated at 100 ohms, which means that at 0, the PT100 RTD has an equivalent resistance value of 100 ohms.

When using PT100 RTD, there are some details that need to be paid attention to. For example, since RTDs have certain requirements for the length of the wire and the instrument to which it is connected, it needs to be used in the correct wiring way so as not to affect the measurement results. In addition, it is necessary to pay attention to the regular calibration of the RTD, and the hidden key bureau to ensure the measurement accuracy.

In a nutshell, the PT100 RTD can be set with a measurement range of -200 to 850 and a rated resistance of 100 ohms. When using, you need to pay attention to the wiring method and calibration issues. <>

PT100 RTD due to different manufacturing processes, its temperature measurement range is also different, ceramic platinum RTD, can measure the widest temperature range, -200 800, now can reach -250 850. Mica platinum RTD, due to the characteristics of mica, its temperature measurement range is -200 420. Due to its packaging and manufacturing characteristics, the temperature range of thin-film platinum RTD is -50 500.

Generally speaking, the three wires of the RTD are connected to the No. 1, No. 2, and No. 3 terminals.

If the display meter has a wiring diagram, the wiring method is shown in the illustration.

If you don't have a wiring diagram or you lose it, wire it as follows:

If there are two wires of the same color for the three wires of the RTD, connect the two wires of the same color to terminal 2 and 3, and the other wire to terminal 1, if the display is abnormal after the power is turned on (display the maximum or minimum), the wire on terminal 1 and the wire on terminal 3 can be swapped.

If the color of the three wires is different, there will inevitably be one of the red, the red wire is connected to the No. 1 terminal, and the remaining two wires are connected to the No. 2 and No. 3 terminals, if the display is not normal after the power is turned on (the maximum or minimum display is displayed), the wire on the No. 1 terminal and the wire on the No. 3 terminal can be replaced.

The wiring method of CU50 and RTD is the same as above.

PT100 has 2 wires There are 3 wires The temperature control meter is generally 3 binding posts, and 2 of the 3 binding posts of the instrument are shorted together on the binding posts, which can be named as the pin, and the other is named 1 by the resistance and the connected oneIf the PT100 2 wire is generally red to 1 pin, the other one is connected to 2 or 3 pins, and shorted. If the red one of the 3 wires of the pt100 is connected to 1 pin, and the other 2 wires of the same color are connected to the pin, there is no order.

Generally speaking, the three wires of the RTD are connected to the No. 1, No. 2, and No. 3 terminals.

If the display meter has a wiring diagram, the wiring method is shown in the illustration.

If you don't have a wiring diagram or you lose it, wire it as follows:

If there are two wires of the same color for the three wires of the RTD, connect the two wires of the same color to terminal 2 and 3, and the other wire to terminal 1, if the display is abnormal after the power is turned on (display the maximum or minimum), the wire on terminal 1 and the wire on terminal 3 can be swapped.

If the color of the three wires is different, there will inevitably be one of the red, the red wire is connected to the No. 1 terminal, and the remaining two wires are connected to the No. 2 and No. 3 terminals, if the display is not normal after the power is turned on (the maximum or minimum display is displayed), the wire on the No. 1 terminal and the wire on the No. 3 terminal can be replaced.

The wiring method of CU50 and RTD is the same as above.

It depends on what kind of meter you are, and the terminal behind the meter is generally clearly marked on it! The instrument of our unit is marked with A, B, B, 3 terminals, and you can directly A, B2 terminals.